Fluids such as plastic material are molded into different configurations. The fluid is passed through apparatus for heating the fluid and for injecting the fluid into the molds. When the fluid solidifies, it forms an article with a shape corresponding to the shape of the molds. It is important that the fluid is heated before it is injected into the molds to insure that the fluid will flow easily into the molds and completely fill the molds before it solidifies.
The injection apparatuses now in use produce articles of like configuration by the thousands. Because of this, it is important to mold the articles as quickly as possible. It would accordingly be desirable to inject fluid into a plurality of cavities simultaneously from a single heating and injecting apparatus. It would additionally be desirable to provide pairs of gates, and the pistons for controlling the fluid to the gates, in a back-to-back in-line relationship in such apparatus to double the number of cavities while maintaining the cavities compact. In such an arrangement, fluid (e.g. resin melt) would flow through one of the passages in one direction in the in-line relationship and fluid would flow through the other passage in the opposite direction in the in-line relationship. The fluid flowing through the passages would then flow through gates in the apparatus to individual cavities within a mold.
To minimize the size of the fluid-injecting apparatus and to increase the number of cavities simultaneously receiving fluid (e.g. resin melt) in a mold from a single injecting apparatus, it would even be desirable to provide for the introduction of fluid through a single inlet and to provide for the flow of fluid simultaneously through a multiple number of passage and then to a multiple number of gates. In such apparatus, it would be desirable to pair the passages, and the pistons for controlling the flow of fluid through the passages to the gates, in a back-to-back in-line relationship.
The desirability of having a multiple number of passages and the associated pistons in a paired back-to-back in-line relationship has been known for some time. However, no one has been able to provide apparatus which provides such a relationship of the passages and the associated pistons satisfactorily in an in-line relationship. The problem of providing such apparatus has been further compounded as a result of the difficulty of providing such apparatus without having fluid leak from the apparatus when the apparatus becomes heated by heaters in the apparatus for heating the fluid.